The main point would to connect the Wealden towns to Brighton.
Ah, so you want exactly the same thing as last time we discussed this, you've just come up with a completely different argument to try to justify "re-open an old line"?
What next?
To be fair, I think the reason why the Horsham line isn't used much a diversionary route is that from 0800-1800 day Sunday the line is a Section 4 possession opportunity meaning that possessions get priority in most casess and there is no Sunday WTT service. The other issue is that not many southern drivers have Dorking to Horsham route knowledge. Some services do get diverted down there though. I think there may also be signalling, staffing issues.
If it's not worth TSGN maintaining route knowledge for London - Horsham - Brighton then I think it safe to assume that the operator wouldn't bother maintaining route knowledge for London - Uckfield - Brighton.
If it's not worth training staff on "via Horsham" route knowledge then I think that speaks volumes about whether "via Uckfield" trains would be running if the BML were closed a couple of weekends a year.
There are also "hidden" flows of traffic from places like Uckfield and Crowborough to Falmer for students and supporters of Brighton & Hove Albion FC
A few football matches a year can pretty much be discounted as a reason for opening a railway.
Your dismissal of Falmer as a village of 500 people is also invalid as it is the main transport link for Sussex University.
...but do those students all live on the Uckfield side of Falmer? Or do they majority live on the Brighton side of Falmer (which already has a frequent train service)?
Whilst I quoted the Waverley Route as one example there are others around the country where the passenger numbers are far more than that estimated
There are three that did much better than expected.
- Tweedbank (line re-opened for political reasons - the LibDems price for coalition at Holyrood - so no need to do much research on passenger numbers - it was going to be built regardless of forecasts)
- Alloa (line re-opened as the price of getting freight off the Forth Bridge - diverting freight through Alloa instead meant noise/disruption for the town so they got a passenger service back in return - passenger forecasts didn't matter)
- Ebbw Vale (line built based on forecast of passengers to Newport - by time it was opened the service was to the much bigger destination of Cardiff instead - this happened at around the same time that the steelworks closed down so a large number of Ebbw Vale people now needed to leave the town each morning for employment reasons)
Meanwhile, there have been a few stations/ lines built that have had fairly underwhelming passenger numbers that don't get discussed much - the Robin Hood line, Airdrie to Bathgate, Larkhall, the original Newcraighall branch, I think Aylesbury Vale Parkway struggled too
But anything that struggles to get the expected passenger numbers gets forgotten about so we can focus on the three lines that bucked the trend.
As enthusiasts we should be supporting any proposals to reopen closed lines.
I'd strongly disagree with that.
We should support the projects that look best - what the railway cannot afford is to spend hundreds of millions of pounds on more loss-making lines that will make it harder to find the money to invest in the projects that we should be focussing on.
Simply backing any and every attempt to open something that was closed in the 1960s is a recipe for disaster.
Heavy rail is great at a limited and specific number of things - generally commuter services into cities and inter-city services.
For other things (like Uckfield to Falmer, or Tavistock to Uckfield etc) a bus is more suitable.
Heavy rail is far too inflexible to be the answer to everything.
There's nothing marginal about the mid-Sussex commuter belt. How long are the trains on the surviving sections now. Nine carriages ?
...because they are running from Uckfield to the place with the biggest demand. That doesn't mean you'd fill nine carriages of passengers wanting to get from Uckfield to Falmer. You know this.
That's a bit silly though really. It's a bit like saying there's no point running my local Hallam line train through to Barnsley and Sheffield because it already runs to Leeds !
Your local "Hallam Line" stopper is fairly busy from Leeds to Castleford and then fairly quiet and then picks up again from Barnsley to Sheffield - the middle bit isn't as busy as each end. That's fine on a route that already exists but I don't think that you'd find much of a business case for a line specifically from Castleford to Barnsley if one didn't exist already.